Specify the maximum number of samples. GIMP gradients allow for complex curves in a number of colour-space co-ordinate systems. In order that these can be converted into SVG's simple RGB linear splines we must sample these complex curves quite densely. The -s option specifies (roughly) the maximum number of samples. In the case that the GIMP gradient is an RGB linear spline gradient the option has no effect, since we can then convert the segments without loss.